Acoustic generator



April 9, 1968 R. R. CHEESEMAN, JR 3,376,847

ACOUSTIC G ENERATOR Filed July 10, 1967 INVENTOR. RICHARD R- CHEESEMAMJR A TTORNE Y United States Patent Ofitice aasignor Minn., a corporation ABSTRACT OF THE DISCLOSURE A whistle utilizing a resonant frequency cavity situated within regions of a jet stream which comprises in addition a rod extended from the cavity into a portion of the jet stream to create fluid flow instability and accentuate the resonant frequency.

The invention The present invention is generally directed to whistles and more particularly directed to a whistle utilizing a rod in a resonant cavity and extending from the resonant cavity into a jet stream which supplies the resonant cavity with vibrational fluid power.

The prior art has many types of whistles extending back many years. However, the prior art either has whistles which utilize resonant cavities without rods contained therein or has cavities situated in the jet stream wherein a rod within the cavity also extends through the jet stream and into the nozzle for producing stability of the jet stream. Another type of whistle utilizes a hole in a plate which is placed in the path of the jet stream so that instability is created on the edges of the hole by the jet stream and produces resonance.

The present invention, however, utilizes the rod to create instability and accentuate the resonant frequency of the cavity within which it is situated so as to produce a more nearly pure tone than the prior art acoustic generators.

It is therefore an object of this invention to provide an improved acoustic generator.

Other objects and advantages of the present invention may be ascertained from a reading of the specification and appended claims along with the single figure which is a cross sectional view of the whistle apparatus.

In the drawing, a nozzle generally designated as has converging lips 12 which form an orifice 13 for changing an incoming low pressure fluid such as air to a high velocity fluid at the orifice 13. The orifice 13 at the end of nozzle 10 is a distance L from the lips of an opening in a container or base 14. Within the base 14 the opening develops into a cavity generally designated as 16. The cavity is generally circular and is of a depth 1 within base 14 dependent upon the frequency desired of the whistle. A dashed line designated as center line extends through the base 14 and the nozzle 10 to show that the preferred embodiment has the nozzle and the cavity lined up on the same center line. A rod 18 is situated on the center line and in the center of cavity 16. As will be noted, the rod 18 extends from the end of cavity 16 by a distance designated as X. For the purposes of this specification by the terminology end or opening of cavity 16, I mean the portion of cavity 16 which is closest to the orifice 13 of nozzle 10.

In operation, a volume of air is supplied under pressure to the entrance portion of the nozzle 10 and converged by portions 12 so as to exit through orifice 13 toward 3,376,847 Patented Apr. 9, 1968 the cavity 16. The exiting fluid Will form a jet stream. The cavity 16 is situated such that instabilities caused by the rod 18 are coincident with the cavity 16. The rod 18 as previously mentioned extends from the end of cavity 16 but does not extend to the outlet of nozzle 10. The rod 18 has sharp edges on the end facing the jet stream in the present embodiment, however, a pointed or rounded rod end has been used also. These edges may be merely corners formed by cutting the rod and squaring off the end thereof or can be somewhat pointed by placing a concave indentation in the end thereof to sharpen the edges of the rod 18 and thereby create instability in the jet stream. The distance X is adjusted so as to create the maximum single frequency sound level of the resonant frequency of cavity 16.

In one working embodiment of the invention, the following dimensions were found to create a substantially pure frequency of approximately 3,000 cycles per second. The distance L was 0.210 inch while the distance X Was 0.095 inch. The depth 1 of the cavity 16 was 0.620 inch while the diameter was inch. The diameter of the rod 18 was 0.031 inch and the diameter of the orifice 13 was 0.064 inch. The pressure of the air at the entrance of the nozzle was approximately 5 p.s.i.g.

Other embodiments of the invention have been produced which have generated acoustic vibrations in the order of 20,000 cycles per second or above and have utilized air pressures as low as 0.3 p.s.i.g.

As previously explained, the depth of cavity 16 is a primary frequency determining means and the extension and diameter of the rod 18 primarily determines the accentuation or level of the sound. However, the diameter of orifice 13, the diameter of cavity 16 and the distance L along with the velocity of the jet stream all contribute to the level of sound and/ or the frequency.

I do not Wish to be limited by the embodiment shown but only by the invention which lies in the use of an instability creating means extending a portion of the distance between a resonant cavity and a fluid nozzle and within a jet stream as claimed in the appended claims wherein:

I claim: 1. Acoustic generator apparatus comprising in combination:

orifice means, as part of a fluid nozzle, for providing a jet stream of fluid;

means including a cylindrical resonator cavity situated a predetermined distance from said orifice means and in the path of said jet stream; and

an instability creating solid rod, having a blunt end and sharp edges, situated in the path of said jet stream and extending from said resonator means only a portion of said predetermined distance toward said orifice means.

2. Apparatus as claimed in claim 1 wherein the rod, the orifice means and the resonator cavity are coaxial.

References Cited UNITED STATES PATENTS 1,812,234 6/1931 Braatelien. 2,519,619 10/1950 Yellott et a1. 116-137 2,788,656 4/1957 Sanders. 3,169,507 2/1965 Rich 116137 3,169,509 2/1965 Rich ll6l37 3,278,165 10/1966 Gafinet 259-1 LOUIS I. CAPOZI, Primary Examiner. 

